Population differentiation in blue orchard bees (Osmia lignaria) observed using multi-locus microsatellite genotypes

Population differentiation in the blue orchard bee (Osmia lignaria) is a concern of pollination biologists due to the increasing traffic of this species for commercial pollination.  The species occurs primarily in the eastern USA and the mountainous western USA, with a large gap in distribution in the Great Plains.  Western populations are fragmented by arid basins and this has led to ecological adaptations in some populations.  Morphological differences have led to subspecific epithets for eastern and western phenotypes.  Despite the wide and fragmented distribution, the known ecological and physiological adaptations, and morphological differentiation, the genetic variation reflecting the differences among populations has been difficult to find.  We sampled bees from four broadly distributed regions to study the genetic differetiation of the species.  We used multilocus microsatellites and Bayesian statistical models to explore the structure of the species across the USA and to understand the potential for genetic introgression resulting from the movement of these bees by commercial producers.